Modeling Energy Consumption and Cost of Semiclosed Greenhouses with Chillers and Dehumidifiers

Evapotranspiration in greenhouse crops is a significant driver of ventilation requirements. As an alternative, semiclosed greenhouses use a chiller with or without a dehumidifier under certain conditions to minimize ventilation and facilitate an increased light use efficiency using carbon dioxide supplementation. An energy model for this type of greenhouse is presented along with simulation results. Using typical meteorological year (TMY) hourly climate data, several locations (Denver, CO, USA; Phoenix, AZ, USA; Toledo, OH, USA; and Portland, OR, USA) are evaluated for suitability of semiclosed operation and the benefits over strictly evaporative cooling systems are quantified. Chillers with dehumidifiers are found to use less energy than chillers with reheat, especially in cooler climates.